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<br />0.1692 inches. This excess results from an assumption that the grasses and fortis <br />will take most of their water from the upper two feet of the medium while the trees <br />and shrubs will take it from the full profile. Thus, with the deeper medium, the <br />available water capacity is much greater than currently exists. <br />It is apparent that the current vegetation is intensely moisture limited, as <br />can be seen by the pattern of grass distribution. Qrasses are widely and evenly <br />distributed over the ground indicating intense moisture cortpetitian between the <br />grasses. This competition is aver what little water is left after the trees and <br />shrubs remove their share. Furthermore, the higher available water capacity of the <br />revegetation medium should permit amore rapid growth of the trees than probably <br />exists in the current vegetation. In short, once established, it is not likely that <br />moisture will al ~s be the limiting factor in the vegetation growth, but other <br />factors such as available light and nutrients will more often be limiting than <br />moisture. Furthermore, the higher level of available water will tend to favor the <br />darker green, cool season grasses over the more gray~reen warm season grasses. <br />This is not to say, however, that moisture will not be a ma,ior factor. <br />Moisture will sometimes be limiting because precipitation at certain times of the <br />year will be too slight to replace the draw produced by the plants. But, the <br />moisture levels, even at their worst, will be far more favorable than is the current <br />condition and therefore the vegetation growth patterns in the mature community <br />should be limited more by available space, light, and nutrients. <br />The final portion of the model calculated the number of trees per acre on the <br />area which is appropriate for trees and predicted final average cover. The <br />calculations are based upon achieving a reclamation standard of the number of trees <br />per acre over the .hole area. That is, if trees are planted to an average density <br />of 35 trees per acre ai 8 acres, what will be the true density on the areas which <br />are actually appropriate for trees? Even more important, once the trees reach a <br />mature size (25 to 50 years) what will the canopy cover be? The canopy cover is <br />vital to the maintenance of a suitable density of grasses to protect the ground <br />against erosion. If canopy cover is too high then grass cover decreases due to <br />decreased available light and this results in more unprotected ground which makes <br />the soil more susceptible to erostan. <br />The first step in this portion of the model determines the characteristics of <br />the existing forest on the site, exclusive of north facing forest areas which are of <br />a different vegetation community. With a density of 74 trees per acre and a tree <br />cover of 35Y. (both are measured values) it was calculated that the average tree <br />PA(~ 3 TREE MODEL STNDER NW PhETmhFTfi EVIDENCE <br />